This invention relates to a method and an apparatus for the real-time measurement of volumetric flows that comprise more than one discrete phase. In particular, the present invention relates to a method and an apparatus for the real-time measurement of two phase or three phase flows from hydrocarbon wells without the requirement of separating the gas, liquids and solids, and without the use of impellers or other similar systems.
In the oil industry, the measurement of multiphase flow is routinely encountered. For example, in order to assess exactly how much oil is being produced, or to improve or restore the productivity of a well, it is required to determine the volumetric flow rates of the individual phases of the material obtained from the well at times throughout the life of the well. A number of methods to measure multiphase flow have been proposed, and they fall into two types. In the first method, a sample of the oil flow is transferred to separators, and the volumes of each phase are determined independently. The problems associated with this method are that a large physical installation is required and that the instantaneous determination of flow is impossible. This specifically limits the analysis of the instantaneous production from a well, or of the volumes of each phase transmitted from the oil fields or offshore sites to the refinery. The second method involves the use of microwave energy, or xcex3-ray radiation, to perform full flow measurement. The microwave and xcex3-ray methods are useful only for homogeneous multiphase fluids. However, the relative volumes of each phase, and the fluid flow rate can both vary considerably as a function of time. As a result, it has been proven that microwave and xcex3-ray methods are not suitable for the measurement of multiphase fluid flow.
It is an object of the present invention to provide a method and apparatus capable of the real-time measurement of volumetric flow rates of different phases in a multiphase fluid flow.
It is another object of the invention to provide a method and apparatus that requires no separate means to determine the volume fraction of the phases of the material in the flow in order to determine the volumetric flow rate.
It is a further object of the invention to provide a method and apparatus that requires no impellers or similar systems to homogenize the flowing multiphase fluid in order to determine the volumetric flow rate of the individual phases.
It is still a further object of the invention to provide a method and apparatus that requires no radiation sources, such as microwave or xcex3-ray, in order to determine the volumetric flow rate of the individual phases.
These and other objects are achieved according to the present invention by providing a novel apparatus and method for the real-time measurement of the flow rate of each separate phase of a multiphase fluid consisting of gas, water and oil. Said apparatus consists of a number of material property (i.e., water, gas, or oil) sensors, temperature sensors, and flow-rate sensors mounted inside a pipe used to transmit the flow. By combining the individual volume fractions of the separate phases with the flow data, the volumetric flow rates of the individual phases in the multiphase fluid are obtained.